Sorry to butt in here, but this is one one those topics that I will fight about UNTIL THE END OF TIME. ;D
Honestly, I do think it's reasonable to infer from canon that if Snape and adult!Harry were placed side-by-side they would immediately begin fucking that Harry is likely the taller of the two. But Snape is just such a larger than life character. Everything about him just screams 'bigger' to me. Plus all those years of being bombarded with images of Rickman and Radcliffe just combine to make it feel wrong to me when Harry is taller than Snape. So much so for me that it always temporarily throws me out of a fic and permanently out of any art regardless of artist or the technical merit of the piece. For me so much of art is visceral and taller!Harry screams WRONG to me even more than seeing an artist draw two right hands, for example. But that's just me. I did want to say, though, that I worked in Child Protective Services for over 20 years and I cannot tell you how many kids who were abused/neglected just shoot up once they are removed from the neglectful environment. Even if they are removed only temporarily and for the first time in their teens. Now, there's no way to know if they actually reached the optimum height they would have otherwise reached, but a number of the kids I saw were the same height or taller than their parents. Imo, for the neglect/abuse to really make a noticeably permanent impact on adult height the abuse had to be far more severe/pervasive than we're shown happening to Harry in canon.